Device for producing liquid from flue gas with low energy consumption and method for using same

A method for using a device for producing liquid from flue gas with low energy consumption, comprising the following steps:

• Pre) providing the device for producing liquid from flue gas with low energy consumption, wherein the device comprises a CO2 and N2 low-temperature medium-pressure adsorption system, an energy utilization system, a low-temperature filtration gas low-temperature compression system, a CO2 low-temperature purification system (101), and a nitrogen liquid device system (100);
• the systems are interconnected through pipelines and valves, wherein the CO2 and N2 low-temperature medium-pressure adsorption system comprises a flue gas cooler (1A), a first gas-liquid separator (1B), a compression system (1C), a drying system (1D), a gas expander system, and a low-temperature medium-pressure adsorption device (1H), which is used to cool, pressurize, dewater, and perform low-temperature adsorption separation of CO2 and N2 from the flue gas;
• the energy utilization system comprises an electric heater (2E), a CO2 compressor (2A), a heat utilizer (2B), and a second cooler (2C), which is used to pressurize, recover heat and cool desorbed gas obtained from the CO2 and N2 low-temperature medium-pressure adsorption system;
• the low-temperature filtration gas low-temperature compression system comprises a low-temperature compressor (3A), which is used for low-temperature pressurization of the low-temperature medium-pressure filtered gas obtained from the CO2 and N2 low-temperature medium-pressure adsorption system, the CO2 low-temperature purification system (101) is used to further purify and liquefy the low-temperature medium-pressure gas obtained from the energy utilization system, to obtain a liquid CO2 product;
• and the nitrogen liquid device system (100) is used to distill and liquefy medium-pressure gas discharged from the low-temperature compression system, to obtain a liquid nitrogen product;
• one end of a flue gas cooler (1A) in the CO2 and N2 low-temperature medium-pressure adsorption system is connected to a flue gas discharge port, while the other end is connected to a first gas-liquid separator (1B), in the first gas-liquid separator (1B), the liquid is discharged through a water outlet (13) of the first gas-liquid separator, and the gas enters the compression system (1C) through a gas outlet (12) of the first gas-liquid separator for compression, cooling, and dewatering, the compressed, cooled, and dewatered flue gas enters the drying system (1D) through a first pipeline (14) to dehydrate and dry thoroughly, so that the flue gas emitted from the drying system (1D) has a water content of ppm level, the drying system (1D) is connected to a expander system, wherein the gas expander system consists of a first expander boosting end (1E), a first cooler (1F), and a gas expansion end (1G), the flue gas with ppm-level water content sequentially enters the first expander boosting end (1E), the first cooler (1F), and the gas expansion end (1G) through the second pipeline (15), the gas expansion end (1G) then enters the low-temperature medium-pressure adsorption device (1H) through a rear third pipeline (18), where the CO2 in the low-temperature medium-pressure flue gas is adsorbed and captured using the low-temperature medium-pressure adsorption principle, a crude CO2 gas with a carbon purity of 85-90% is obtained at a desorption gas outlet (19) of the low-temperature medium-pressure adsorption device, and a medium-pressure crude nitrogen gas with a CO2 concentration of less than 1 ppm is obtained at the low-temperature medium-pressure filtered gas outlet (20) of the low-temperature medium-pressure adsorption device;
• the nitrogen purity of the medium-pressure crude nitrogen gas is 87-93%, thus achieving the purpose of carbon nitrogen separation, the low-temperature medium-pressure filtered gas outlet (20) is also connected to the low-temperature medium-pressure adsorption device (1H) through a fourth pipeline (32), so that a portion of the low-temperature filtered gas enters the low-temperature medium-pressure adsorption device (1H) through the fourth pipeline (32) as cold-blowing regeneration gas, to cold-blow the adsorbent in the low-temperature medium-pressure adsorption device (1H);
• the desorption gas outlet (19) of the low-temperature medium-pressure adsorption device is connected to the CO2 compressor (2A) in the energy utilization system, to compress and boost the crude CO2 gas;
• the CO2 compressor (2A) is sequentially connected to the heat utilizer (2B), the second cooler (2C), and the CO2 low-temperature purification system (101), the second cooler (2C) further cools the cooled and pressurized crude CO2 gas, such that the pressurized crude CO2 gas exiting from the second cooler (2C) meets the temperature and pressure requirements of the CO2 low-temperature purification system (101), the CO2 low-temperature purification system (101) is used to purify and refine the pressurized low-temperature CO2, yielding industrial-grade or food-grade CO2, the CO2 low-temperature purification system (101) is connected to the heat utilizer (2B) through a ninth pipeline (24), and the heat utilizer (2B) is connected to the fourth pipeline (32) of the low-temperature medium-pressure adsorption device (1H), to heat the low-temperature regeneration gas exiting from the CO2 low-temperature purification system (101), which then enters the low-temperature medium-pressure adsorption device (1H) as heated regeneration gas;
• the low-temperature medium-pressure filtered gas outlet (20) of the low-temperature medium-pressure adsorption device is sequentially connected to the low-temperature compressor (3A) and the nitrogen liquid device system (100) in the low-temperature filtered gas compression system at the rear, to pressurize all or most of the low-temperature filtered gas, which then enters the nitrogen liquid device system (100), the nitrogen liquid device system (100) is used to further refine and liquefy the pressurized low-temperature filtered gas to obtain the liquid nitrogen product, a tenth pipeline (26) is arranged at the rear of the nitrogen liquid device system (100), the tenth pipeline (26) is branched into two routes at the rear, one route is sequentially connected to the heat utilizer (2B) and the electric heater (2E), the electric heater (2E) is connected to a sixth pipeline (102), and the sixth pipeline (102) is connected to the drying system (1D), to heat the waste gas regeneration gas from the nitrogen liquid device system (100) to a required temperature before entering the drying system (1D) as the regeneration gas for heating, the other route of the tenth pipeline (26) is directly connected to the sixth pipeline (102), to feed the waste gas regeneration gas from the nitrogen liquid device system (100) to directly enter the drying system (1D) as cold blow gas for cold blowing;
• the CO2 low-temperature purification system (101) comprises a third condenser (4F), an evaporator (4D), a liquefier (4E), and a third distillation column (4G), wherein the third condenser (4F) is mounted above the third distillation column (4G), and the evaporator (4D) is mounted below the third distillation column (4G), the liquefier (4E) is arranged separately outside the column;
• the second cooler (2C) is connected to the evaporator (4D), and the evaporator (4D) is connected to the liquefier (4E), the liquefier (4E) is connected to the third distillation column (4G) through an eighth pipeline (46);
• the third distillation column (4G) is connected to the third condenser (4F), and the third condenser (4F) is connected to the third distillation column (4G) through a seventh pipeline (110) to form a closed loop, a condensation liquid inlet channel (48) and a condensation gas outlet channel(49) are formed in the third condenser (4F), a ninth pipeline (24) is provided below the third distillation column (4G) and is connected to the heat utilizer (2B), a fifth pipeline (47) is provided at the bottom of the third distillation column (4G) for obtaining the liquid CO2 product;
• the nitrogen liquid device system (100) comprises a circulating compression system, a high and low-temperature gas expander, a heat exchanger (5A), a second gas-liquid separator (5H), a distillation column system, and a subcooler, the circulating compression system consists of a first compressor (5K1) and a second compressor (5K2), the high and low-temperature gas expander is equipped with a second expander boosting end (5P), a first expansion end (5T), and a second expansion end (5U), the subcooler consists of a first subcooler (5D), a second subcooler (5F), and a third subcooler (5J), the distillation column system consists of a first distillation column (5B) and a second distillation column (5E), wherein a first condenser (5C) is mounted above the first distillation column (5B), and a second condenser (5G) is mounted above the second distillation column (5E), the low-temperature compressor (3A) is sequentially connected to the heat exchanger (5A) and the first distillation column (5B), the first distillation column (5B) is provided with two branch pipelines, wherein the first branch of the first distillation column (5B) is sequentially connected to the first subcooler (5D), the first condenser (5C), the second distillation column (5E), the second subcooler (5F), and the second condenser (5G), the second condenser (5G) is sequentially connected to the second subcooler (5F), the first subcooler (5D), and the heat exchanger (5A) through pipelines at the top;
• the heat exchanger (5A) is connected to the tenth pipeline (26) for the regeneration of the drying system (1D), the second branch pipeline of the first distillation column (5B) is directly connected to the first condenser (5C) and the heat exchanger (5A) separately;
• the first condenser (5C) is also provided with two branch pipelines, wherein the first branch pipeline of the first condenser (5C) is connected to the first distillation column (5B), and the second branch pipeline of the first condenser (5C) is connected to the second gas-liquid separator (5H);
• the second distillation column (5E) is provided with two branches, wherein the first branch of the second distillation column (5E) is connected to the second condenser (5G), and the second branch of the second distillation column (5E) is connected to the heat exchanger (5A);
• the second condenser (5G) is also provided with two branches, wherein the first branch of the second condenser (5G) is connected to the second distillation column (5E), and the second branch of the second condenser (5G) is sequentially connected to the second gas-liquid separator (5H) and the third subcooler (5J);
• one end of the third subcooler (5J) is connected to the liquid nitrogen product channel, and the other end is connected to the heat exchanger (5A) through a first throttle valve (V4) through the third subcooler (5J), the second gas-liquid separator (5H) is connected to the heat exchanger (5A), and the heat exchanger (5A) is sequentially connected to the first compressor (5K1) and the second compressor (5K2), the second compressor (5K2) is provided with two branches, wherein the first branch of the second compressor (5K2) is sequentially connected to the high and low-temperature gas expander (5P), the heat exchanger (5A), and the second expansion end (5U), and finally connected to the second gas-liquid separator (5H) for circulation through the second expansion end (5U), the second branch of the second compressor (5K2) is sequentially connected to the heat exchanger (5A), the first expansion end (5T), the heat exchanger (5A), and finally connected to the first compressor (5K1) for circulation through the heat exchanger (5A), the heat exchanger (5A) is directly connected to the second gas-liquid separator (5H), and a second throttle valve (V3) is provided on the connecting pipeline, using the low-temperature distillation principle, the low-temperature nitrogen-containing gas obtained from the low-temperature compressor (3A) is further purified and liquefied, so as to obtain the liquid nitrogen product;
• 1) Flue gas pre-treatment:
• Performing compression, cooling, dewatering, and drying treatment on the flue gas, wherein the water content of the treated flue gas is less than 1 ppm;
• 2) Coarse separation of CO2 and N2 gases:
• Introducing the gas from the step 1) into the gas expander system to obtain crude carbon dioxide gas with a carbon purity of 85-90%, and medium-pressure crude nitrogen gas with a carbon dioxide concentration of less than 1 ppm, wherein the nitrogen purity of the medium-pressure crude nitrogen gas is 87-93%;
• 3) Purification and liquefaction to obtain the liquid CO2 product
• Introducing the crude CO2 gas with a carbon purity of 85-90% obtained from the step 2) into the CO2 low-temperature purification system (101) to obtain the liquid CO2 product;
• and
• 4) Purification and liquefaction to obtain the liquid N2 product:
• Introducing the medium-pressure crude nitrogen gas with a carbon dioxide concentration of less than 1 ppm obtained from the step 2) into the nitrogen liquid device system (100) to obtain the liquid N2 product.